[TableGen] Use StringRef::compare instead of != and <. NFC.

The previous code would always do 1 or 2 prefix compares;
explicitly only do one.

This speeds up debug -gen-asm-matcher by ~10% (e.g. X86: 40s -> 35s).

llvm-svn: 273583

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/utils/TableGen/AsmMatcherEmitter.cpp b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
index 19bb0b4c805..76228e0b658 100644
--- a/llvm/utils/TableGen/AsmMatcherEmitter.cpp
+++ b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
@@ -579,8 +579,8 @@ struct MatchableInfo {
   /// operator< - Compare two matchables.
   bool operator<(const MatchableInfo &RHS) const {
     // The primary comparator is the instruction mnemonic.
-    if (Mnemonic != RHS.Mnemonic)
-      return Mnemonic < RHS.Mnemonic;
+    if (int Cmp = Mnemonic.compare(RHS.Mnemonic))
+      return Cmp == -1;
 
     if (AsmOperands.size() != RHS.AsmOperands.size())
       return AsmOperands.size() < RHS.AsmOperands.size();